Session IB

Monday, May 16th

Session IB

T6

Strategy
for Creating Modified Microarrays on Porous Silicon

Sidney G. Coombs, Sitora Khodjaniyazova,
and Frank V. Bright

University at Buffalo, Department of Chemistry

Porous
silicon (pSi) exhibits strong, visible photoluminescence (PL) at room
temperature. One negative aspect of as-prepared, H-passivated, pSi (ap-pSi) is
that the PL is unstable. The goal of our research is to stabilize the PL and
simultaneously impart chemical functionality to the pSi surface through
silanization with an organically modified silane. We are particularly
interested in creating silane-modified microarrays on pSi which are candidates for
lab-on-a-chip and simultaneous multi-analyte detection. Our previous work
showed, through combined PL and Fourier transform infrared (FT-IR) imaging
studies, that ap-pSi can be directly modified by contact pin-printing (CPP)
organosilane arrays using a solid W pin (pin diameter, PD = 200 μm). In the
case of the popular organosilane 3-aminopropyltriethoxysilane (APTES), results
showed that APTES-derived spots form and rapidly spread to 5x PD after CPP on
pSi. At-a-glance, this result suggests that APTES is a poor candidate for
preparing microarrays on pSi where larger spots negatively impact spot density;
however, spatial composition of APTES-derived spots turns out to be crucial. In
this presentation, we discuss the discovery of distinct regions within APTES-derived
spots on pSi and the impacts of this discovery on achievable microarray spot
densities. We will demonstrate that spatially isolated APTES-modified spots and
even bioconjugate spots can be prepared on pSi with as little as 2.5x PD
interspot spacing.

T7

Unraveling
the Structure of Apo-metallothionein Using ESI-MS and Selective Cysteine Modification

Gordon Irvine and Prof. Martin Stillman

The University of Western Ontario

Metallothioneins
(MTs) are a family of small, cysteine-rich, metal binding proteins whose major
biological function is thought to be controlling zinc and copper homeostasis in
addition to cadmium, lead and mercury detoxification. Able to bind up to 7
divalent metals either terminally or through bridging coordination, the structure
of MT remains elusive as only the fully metalated forms have been studied by
NMR and X-ray crystallography. The partially-metalated and apo forms of MT are
more biologically relevant and can shed light of the mechanistic details of
metal binding. In this talk, I will highlight our most recent attempts to probe
the structural characteristics of apo-MTs using covalent cysteine modifications
coupled with ESI-MS. Our results show previously unreported structure in
metal-free MT confirmed with similar results from multiple modifying agents.
This new data force us to reconsider the model of apo-MT being a fluxional
peptide with no structure. We can now think of the apo-protein as being
"primed" for metal binding and a loosely held globular structure.

Crystalline
Si (c-Si) plays an important role in the semiconductor industry and its
crystallinity is key to product performance. As a result, quality assurance of
these materials is very important. We
have assessed the nanocrystalline Si (nc-Si) homogeneity throughout amorphous
Si (a-Si) agglomerates by using Raman spectroscopic mapping. We monitored the
Raman band position and shape by using a peak-fitting algorithm for the
transverse optical phonon mode for a-Si at 480 cm-1, nc-Si between
500 and 517 cm-1, and c-Si at 520.7 cm-1. We report
preliminary findings investigating nc-Si homogeneity in these agglomerates by
using atomic force microscopy, photoluminescence and Raman spectroscopic
mapping.

T9

Investigation
of PBDE-47 and its Hydroxylated Analog, 5-OH-BDE-47, in Humans: Metabolic or Environmental
Impact?

Understanding sources of hydroxylated brominated diphenyl ethers
(OH-BDEs) in humans has been under investigation for the past decade due to
their neurotoxic and endocrine disrupting effects. There are two pathways for
OH-BDEs exposure in humans, (1) metabolites of the polybrominated diphenyl
ether (PBDE) flame retardants, and (2) consumption via dietary intake and
occupational exposure. In vitro studies demonstrated that the most predominant
PBDE congener, PBDE-47, is metabolized in the body into 5-OH-BDE-47 by the
CYP2B6 enzyme. However, the activities of the allelic isoforms of CYP 2B6 (i.e.
CYP2B6*1, CYP2B6*4, CYP2B6*5, CYP2B6*46 CYP2B6*7, and CYP2B6*18) vary among
individuals, and can be a key insight in determining the source for the levels
of 5-OH-BDE-47 in humans. The goal of this study is to quantify 5-OH-BDE-47 and
PBDE-47 in blood from a cohort of 25 women from the United States. The two most
common CYP 2B6 isoforms expressed were CYP2B6*1 and CYP2B6*6, and thus were
compared here in relation to their PBDE-47 and 5-OH-BDE-47 concentrations.
Women with the CYP2B6 *6 allele (n=8) showed good correlation between PBDE-47
and 5-OH-BDE-47 levels with an R2= 0.83, however the CYP2B6*1 allele
(n= 12) showed almost no correlation (R2= 0.06) between these two
congeners. Given that the average levels
of OH-BDEs in the women with the *1 and *6 alleles were not statistically
different, it is evident that accumulation of OH-BDEs in humans is not solely
based on biological metabolism, but also dependent on other environmental
sources as well.